Stent with support braces

ABSTRACT

A stent includes expandable rings formed from a plurality of interconnected struts. A plurality of bridges couple adjacent rings together. The bridges are connected to adjacent rings at first and second connection points, and a first brace element is disposed therebetween. The first connection point is circumferentially offset relative to the second connection point so that the bridge is transverse to the longitudinal axis of the stent. The first brace element of one bridge engages an adjacent bridge or a brace element of the adjacent bridge when the corresponding adjacent rings are in the contracted configuration thereby providing additional support and rigidity to the stent to lessen buckling of the stent during loading onto a delivery catheter or during deployment therefrom.

CROSS-REFERENCES TO RELATED APPLICATIONS

The present application claims the benefit of U.S. ProvisionalApplication No. 61/386,337, filed on Sep. 24, 2010. The presentapplication is related to U.S. patent application Ser. No. 12/949,609filed on Nov. 18, 2010. The foregoing applications are herebyincorporated by reference herein in their entirety.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates generally to medical devices, and moreparticularly to endoluminal prostheses such as stents, or otherimplantable structures. The prostheses may be placed in the arterialsystem, the venous system, or any other portion of the body. The use ofstents may also be used to deliver drugs to tissue, support tissue, ormaintain patency of body lumens, as well as performing other functions,and have been widely reported in the scientific and patent literature.

Stents are typically delivered via a catheter in an unexpandedconfiguration to a desired location in the body. The combined stent andcatheter is typically referred to as the stent delivery system. Once ata desired location, the stent is expanded and implanted into the bodylumen. Examples of locations in the body include, but are not limitedto, arteries (e.g. aorta, coronary, carotid, cranial, iliac, femoral,etc.), veins (e.g. vena cava, jugular, iliac, femoral, hepatic,subclavian, brachiocephalic, azygous, cranial, etc.), as well as otherlocations including the esophagus, biliary duct, trachea, bronchials,duodenum, colon, and ureter.

Typically, a stent will have an unexpanded configuration with reduceddiameter for delivery and an expanded configuration with expandeddiameter after placement in the vessel, duct, or tract. Some stents areself-expanding, and some stents are mechanically expanded with a radialoutward force applied from within the stent (e.g. with a balloon). Somestents have one or more characteristics common to both self-expandingand mechanically expandable stents.

Self-expanding stents are made from a material that is resilientlybiased to return to a pre-set shape. These materials may includesuperelastic and shape memory materials that can expand to an implantedconfiguration upon delivery or through a change in temperature.Self-expanding stents are constructed from a wide variety of materialsincluding Nitinol (a nickel titanium alloy), spring steel, shape-memorypolymers, etc.

In many stent delivery systems, particularly those used to deliver aself-expanding stent, the stent is typically retained on the catheter inits unexpanded form with a constraining member or other retention devicesuch as a sheath or outer shaft. The stent may be deployed by retractingthe outer shaft from over the stent. To prevent the stent from beingdrawn longitudinally with the retracting shaft, many delivery systemsprovide the catheter shaft with a pusher, bumper, hub, holder or otherstopping element.

Precise delivery of stents can be challenging. In the case of balloonexpandable stents, the stent may foreshorten as the stent radiallyexpands, therefore, the change in length must be taken into account whendeploying the stent at the treatment site. In the case of self-expandingstents, due to the elastic nature of the stents, they may “jump” awayfrom the delivery catheter during deployment. Additionally, depending onthe anatomy being treated, this may add further challenges to accuratestent delivery. In certain parts of the anatomy, longer stents may beneeded to treat longer lesions or treatment regions. For example, withilio-femoral and ilio-caval stenting, much longer stents are oftenrequired as compared with stenting of coronary lesions. This type ofvenous stenting may be used for the treatment of iliac vein compressionsyndrome (IVCS) and post-thrombotic syndrome (PTS) whereby the profundaand the inferior vena cava can be partially or completely blocked (or“stent jailed”) by the stent if the stent is not placed accurately afterdeployment. Because the stents are longer, they are often more difficultto load and onto a delivery catheter, and they may buckle during theloading process when a radial force is applied to the stent to reduceits diameter.

Additionally, deployment forces of radially strong or large diameterself expanding stents can be relatively high. Furthermore, deploymentforces can be equally high with stents that are longer in length due tothe added friction between stent and a constraining or protectivesheath. These high deployment forces may cause the stent to axially orradially buckle when loaded or deployed because the longer stents areless supported and less rigid, they can also buckle during deployment.This is of particular concern when long self-expanding stents are used.

Providing a stent that avoids or has reduced potential for bucklingduring delivery allows the stent to overcome the excessive friction andavoid the bind up of the device during stent release. This is alsodesirable since incomplete or incorrect release of stent may require theuser to remove the delivery system from the body at which time the stentmay be unintentionally deployed in an undesirable location.

Therefore, it would be desirable to provide a stent used for treatinglonger lesions or longer treatment regions that has greater structuralsupport and rigidity in order to resist buckling or unwanted deformationduring loading onto a delivery system or during deployment in a patient.

At least some of these objectives will be met by the inventionsdescribed herein.

2. Description of the Background Art

Relevant patents and publications include U.S. Pat. Nos. 5,755,776;6,261,318; 6,605,110; 6,749,629; 6,929,660; 7,122,049; 7,611,531;7,722,661; and U.S. Patent Publication Nos. 2004/0204752; 2005/0116751;2007/0055348; 2007/0255387; and 2009/0163989.

BRIEF SUMMARY OF THE INVENTION

The present invention relates generally to medical devices, and moreparticularly to endoluminal prostheses such as stents, or otherimplantable structures. The stents may be deployed in the arterialsystem, the venous system, or any other portion of the body.

In a first aspect of the present invention, a stent comprises aplurality of radially expandable rings each having a contractedconfiguration suitable for delivery and a radially expandedconfiguration for engaging and supporting tissue. Each ring is formedfrom a plurality of interconnected struts, with adjacent struts in eachring being connected together with a connector, and each ring having aproximal end, and a distal end. The plurality of rings is coaxiallyaligned with one another to form a longitudinal axis. A distal end ofone ring faces a proximal end of an adjacent ring. The stent also has aplurality of bridges disposed between adjacent rings. The plurality ofbridges couple adjacent rings together. One or more of the bridgescomprise a first end, a second end, and a first brace elementtherebetween. The first end of the bridge is coupled with the distal endof a first ring at a first connection point, and the second end of thebridge is coupled with the proximal end of an adjacent second ring at asecond connection point. The first connection point may becircumferentially offset relative to the second connection point so thatthe bridge is transverse to the longitudinal axis. The first braceelement of one bridge engages an adjacent bridge or a brace element ofthe adjacent bridge when the corresponding adjacent rings are in thecontracted configuration thereby providing additional support andrigidity to the stent to lessen buckling of the stent during loadingonto a delivery catheter or during deployment therefrom.

The plurality of interconnected struts may form a series of peaks andvalleys. The peaks and valleys of a first ring may be in phase with thepeaks and valleys of an adjacent ring. The connector that interconnectsthe plurality of struts may be U-shaped or V-shaped. The rings may beself-expanding, balloon expandable, or a combination thereof.

The one or more bridges may comprise a first arm and a second arm, andthe brace may be disposed therebetween. The first arm or the second armmay comprise a linear strut. The first arm or the second arm maycomprise a width, and the first brace element may comprise a width widerthan the width of the first or second arm. The first connection pointmay be a peak of one ring, and the second connection point may be on avalley of an adjacent ring. The first connection point may be on theapex of the peak, and the second connection point may be on the bottomof the valley.

A bridge element may couple each pair of adjacent struts interconnectedtogether in a first ring with a pair of adjacent struts interconnectedtogether in an adjacent second ring or an adjacent third ring. The firstbrace element may comprise a rectangular region, a parallelogram shapedregion, or a serpentine shaped region, and may also comprise an upperengagement surface and a lower engagement surface. The upper engagementsurface may engage a lower engagement surface on an adjacent braceelement when the corresponding rings are in the collapsed configuration.The upper and lower engagement surfaces may comprise flat planarsurfaces. The upper engagement surface may have a first contour and thelower engagement surface on the adjacent brace may have a secondcontour, and the first contour may nest within the second contour.

The one or more bridges may comprise a plurality of bridges each havinga brace element. The bridges may join the two adjacent rings together,and the brace elements on each bridge may be axially aligned with oneanother to form a circumferentially oriented column of braces. The braceelements on each bridge may be circumferentially aligned with oneanother to form an axially oriented row of braces. The brace on a firstbridge may be axially offset relative to a brace on the adjacent ringthereby forming a staggered pattern of braces. The braces may also bearranged to form a circumferentially staggered pattern.

A first bridge may couple a first ring and a second adjacent ring, and asecond bridge may couple the second ring with a third ring adjacent thesecond ring. The first bridge may have a first slope, and the secondbridge may have a second slope opposite the first bridge. The firstbrace element may not contact a brace element of an adjacent bridge whenthe corresponding rings are in the radially expanded configuration. Theplurality of bridges may be disposed between adjacent rings and may besubstantially parallel with one another.

One or more of the bridges may comprise a length, and the first braceelement comprises a length shorter than the bridge length. The one ormore bridges may comprise a second brace element or a plurality of braceelements, and the brace elements may be separated from the first bridgeby a strut. The one or more bridges may comprise a plurality of bridgeseach having a first brace and a second brace separated by a strut. Theplurality of bridges may join two adjacent rings together, and the firstand second brace elements on each bridge may be circumferentiallyaligned with one another, thereby forming a first column ofcircumferentially oriented brace elements and a second column ofcircumferentially oriented brace elements.

The first brace element may comprise a slotted region extending throughthe entire thickness of the brace element. The first brace element maycomprise a solid tab without slots extending therethrough. A pair ofbridges each having a brace element and joining two adjacent rings maybe separated by a bridge without a brace element and joining the twoadjacent rings. At least some of the plurality of interconnected strutsmay remain unconnected with a bridge. At least some of the bridges maycomprise a brace element having a tapered proximal or distal end.

In another aspect of the present invention, a method for delivering aprosthesis may comprise providing a stent comprising a plurality ofradially expandable rings interconnected with a plurality of bridges,wherein some of the bridges comprise a brace element. The stent isloaded onto a delivery catheter, and is supported during the loading.Supporting the stent may comprise engaging brace elements on adjacentbridges against one another. The stent is deployed from the deliverycatheter.

Loading the stent may comprise crimping the stent onto the deliverycatheter. The stent may comprise a diameter, and the crimping step mayreduce the diameter. Loading the stent may comprise applying a radialforce against the stent.

Each brace element may comprise an upper surface and a lower surface,and engaging brace elements may comprise nesting the upper surface ofone brace element with a lower surface of an adjacent brace element.Supporting the stent may reduce or eliminate buckling of the stentduring loading.

Deploying may comprise retracting a sheath away from the stent so thatthe stent is unconstrained from radial expansion. Deploying may compriseself-expanding the stent or balloon expanding the stent. Deploying thestent may comprise deploying the stent into a vein to alleviatecompression of a portion of the vein.

The method may further comprise rigidifying the stent during thedeployment. Rigidifying may comprise engaging brace elements on adjacentbridges against one another. Rigidifying may comprise applying anaxially oriented force to the stent, thereby resulting in theengagement. Rigidifying the stent may reduce or eliminate buckling ofthe stent during deployment.

The engaged brace elements may disengage from one another during orafter the deployment.

In another aspect of the invention, a stent comprises a plurality ofradially expandable rings each having a contracted configurationsuitable for delivery and a radially expanded configuration for engagingand supporting tissue. Each ring is formed from a plurality ofinterconnected struts, adjacent struts in each ring being may beconnected together with a connector, and each ring has a proximal end,and a distal end. The plurality of rings is coaxially aligned with oneanother to form a longitudinal axis. A distal end of one ring faces aproximal end of an adjacent ring. The stent also has a plurality ofbridges disposed between adjacent rings. The plurality of bridges maycouple adjacent rings together. One or more of the bridges comprise afirst end, a second end, and a first brace element therebetween. Thefirst end of the bridge is coupled with the distal end of a first ringat a first connection point, and the second end of the bridge may becoupled with the proximal end of an adjacent second ring at a secondconnection point. The first brace elements are aligned in single column.Each brace element has a proximal end and a distal end, the proximal endand distal end of each brace element has a tapered shape. The firstbrace element of one bridge engages an adjacent bridge or a braceelement of the adjacent bridge when the corresponding adjacent rings arein the contracted configuration.

The plurality of interconnected struts may form a series of peaks andvalleys. The first connection point is on a peak of one ring, and thesecond connection point is on a valley of an adjacent ring. The peaksand valleys of a first ring may be in phase with the peaks and valleysof an adjacent ring. The connector interconnecting the plurality ofstruts may be U-shaped or V-shaped.

The rings of the stent may be self-expanding and may be balloonexpandable. The first connection point may be circumferentially offsetrelative to the second connection point so that the bridge is transverseto the longitudinal axis. The one or more bridges comprise a first armand a second arm, and the brace is disposed therebetween. The first armor the second arm may comprise a linear strut. The first arm or thesecond arm may comprise a width, and the first brace element compriseswidth wider than the width of the first or second arm. The firstconnection point may be on a peak of one ring, and the second connectionpoint may be on a valley of an adjacent ring. The first connection pointmay be on the apex of the peak. The second connection point may be onthe bottom of the valley.

A bridge element may couple each pair of adjacent struts interconnectedtogether in a first ring with a pair of adjacent struts interconnectedtogether in an adjacent second ring or an adjacent third ring. The firstbrace element comprises a parallelogram shaped region, and may comprisean upper engagement surface and a lower engagement surface. The upperengagement surface may engage a lower engagement surface on an adjacentbrace element when the corresponding rings are in the collapsedconfiguration. The upper engagement surface and the lower engagementsurface may comprise planar surfaces. The upper engagement surface mayhave a first contour and the lower engagement surface on the adjacentbrace may have a second contour, the first contour nesting with thesecond contour.

The one or more bridges may comprise a plurality of bridges each havinga brace element. The bridges may join the two adjacent rings together.The brace elements on each bridge may be axially aligned with oneanother to form a circumferentially oriented column of braces. The braceelements on each bridge may be circumferentially aligned with oneanother to form an axially oriented row of braces. The brace on a firstbridge may be axially offset relative to a brace on the adjacent ring.The braces may form a circumferentially staggered pattern.

A first bridge may couple a first ring and a second adjacent ring, and asecond bridge may couple the second ring with a third ring adjacent thesecond ring. The first bridge may have a first slope, and the secondbridge may have a second slope opposite the first bridge. The firstbrace element may not contact a brace element of an adjacent bridge whenthe corresponding rings are in the radially expanded configuration. Theplurality of bridges disposed between adjacent rings may comprise aplurality of bridges substantially parallel with one another.

One or more bridges may comprise a length, and the first brace elementmay comprise a length shorter than the bridge length. The one or morebridges may comprise a plurality of brace elements. A pair of bridgeseach having a brace element and joining two adjacent rings may beseparated by a bridge without a brace element and joining the twoadjacent rings. At least some of the plurality of interconnected strutsmay remain unconnected with a bridge. At least some of the bridges maycomprise a brace element having a rounded proximal or distal end.

In another aspect of the invention, a stent comprises a plurality ofradially expandable rings each having a contracted configurationsuitable for delivery and a radially expanded configuration for engagingand supporting tissue. Each ring is formed from a plurality ofinterconnected struts, adjacent struts in each ring being connectedtogether with a connector, and each ring having a proximal end, and adistal end. The plurality of rings is coaxially aligned with one anotherto form a longitudinal axis. A distal end of one ring faces a proximalend of an adjacent ring. The stent also has a plurality of bridgesdisposed between adjacent rings. The plurality of bridges couplesadjacent rings together. One or more of the bridges comprise a firstend, a second end, and a first brace element therebetween. The first endof the bridge is coupled with the distal end of a first ring at a firstconnection point, and the second end of the bridge is coupled with theproximal end of an adjacent second ring at a second connection point.The plurality of brace elements are aligned in single column. Each braceelement has a serpentine shape that includes a plurality of curvedportions. The first brace element of one bridge engages an adjacentbridge or a brace element of the adjacent bridge when the correspondingadjacent rings are in the contracted configuration.

The plurality of interconnected struts may form a series of peaks andvalleys. The peaks and valleys of a first ring may be in phase with thepeaks and valleys of an adjacent ring. The connector interconnecting theplurality of struts may be U-shaped or V-shaped. The rings may beself-expanding, balloon expandable, or a combination thereof.

The first connection point may be circumferentially offset relative tothe second connection point so that the bridge is transverse to thelongitudinal axis. The first connection point may be on a peak of onering, and the second connection point may be on a valley of an adjacentring. The first connection point may be on the apex of the peak. Thesecond connection point may be on the bottom of the valley.

The one or more bridges comprise a first arm and a second arm, and thebrace is disposed therebetween. The first arm or the second arm maycomprise a linear strut. The first arm or the second arm may compriseangled ends. The first arm or the second arm may comprise a width, andthe first brace element may comprise a width wider than the width of thefirst or second arm.

A bridge element may couple each pair of adjacent struts interconnectedtogether in a first ring with a pair of adjacent struts interconnectedtogether in an adjacent second ring or an adjacent third ring. The firstbrace element may comprise an upper engagement surface and a lowerengagement surface, such that the upper engagement surface engages alower engagement surface on an adjacent brace element when thecorresponding rings are in the collapsed configuration. The upperengagement surface and the lower engagement surface comprise planarsurfaces. The brace elements on each bridge may be axially aligned withone another to form a circumferentially oriented column of braces. Thebrace elements on each bridge may be circumferentially aligned with oneanother to form an axially oriented row of braces.

A first bridge may couple a first ring and a second adjacent ring, and asecond bridge may couple the second ring with a third ring adjacent thesecond ring. The first bridge may have a first slope, and the secondbridge may have a second slope opposite the first bridge. The pluralityof bridges disposed between adjacent rings may comprise a plurality ofbridges substantially parallel with one another. The one or more bridgesmay comprise a length, and the first brace element comprises a lengthshorter than the bridge length. The one or more bridge may comprise aplurality of brace elements.

In another aspect of the present invention, a stent comprises aplurality of radially expandable rings each having a contractedconfiguration suitable for delivery and a radially expandedconfiguration for engaging and supporting tissue. Each ring is formedfrom a plurality of interconnected struts, each ring having a proximalend and a distal end.

The plurality of rings is coaxially aligned with one another to form alongitudinal axis. A distal end of one ring faces a proximal end of anadjacent ring. The stent also has a plurality of bridges disposedbetween adjacent rings. The plurality of bridges couples adjacent ringstogether. One or more of the bridges comprise a first end and a secondend. The first end of the bridge is coupled with the distal end of afirst ring at a first connection point, and the second end of the bridgeis coupled with the proximal end of an adjacent second ring at a secondconnection point. A first bridge engages an adjacent bridge of theplurality of bridges when the corresponding adjacent rings are in thecontracted configuration.

The plurality of struts may include an upper strut and a lower strutconnected at a first strut end and forming an opening at a second strutend. The plurality of interconnected struts may form a series of peaksand valleys. The first connection point is on a peak of one ring, andthe second connection point is on a valley of an adjacent ring. Thepeaks and valleys of a first ring may be in phase with the peaks andvalleys of an adjacent ring. The connector interconnecting the pluralityof struts may be U-shaped or V-shaped.

The rings of the stent may be self-expanding and may be balloonexpandable. The first connection point may be circumferentially offsetrelative to the second connection point so that the bridge is transverseto the longitudinal axis. The one or more bridges may comprise a firstarm extending the full length of the bridge.

The first connection point may be on a peak of one ring, and the secondconnection point may be on a valley of an adjacent ring. The firstconnection point may be on the apex of the peak. The second connectionpoint may be on the bottom of the valley.

A bridge element may couple each pair of adjacent struts interconnectedtogether in a first ring with a pair of adjacent struts interconnectedtogether in an adjacent second ring or an adjacent third ring. A bridgemay couple a first ring and a second adjacent ring, and a second bridgemay couple the second ring with a third ring adjacent the second ring.The first bridge has a first slope, and the second bridge has a secondslope opposite the first bridge. A plurality of bridges disposed betweenadjacent rings may comprise a plurality of bridges substantiallyparallel with one another. At least some of the plurality ofinterconnected struts remain unconnected with a bridge.

These and other embodiments are described in further detail in thefollowing description related to the appended drawing figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an exemplary embodiment of a braced stent in aradially collapsed configuration.

FIG. 2 illustrates the stent of FIG. 1 in a radially expandedconfiguration.

FIG. 3 illustrates another exemplary embodiment of a braced stent.

FIG. 4 illustrates still another exemplary embodiment of a braced stenthaving multiple braces on a bridge.

FIG. 5 illustrates an exemplary embodiment of a braced stent having abrace element with a slotted region.

FIG. 6 illustrates an exemplary embodiment of a stent having staggeredbrace elements.

FIG. 7 illustrates an exemplary embodiment of a stent with alternatingbrace elements.

FIG. 8 illustrates another exemplary embodiment of a stent havingalternating brace elements.

FIG. 9A illustrates still another exemplary embodiment of a stent havingmultiple brace elements on a connector.

FIG. 9B illustrates another exemplary embodiment of a stent having asingle brace element on a connector.

FIG. 10 illustrates yet another exemplary embodiment of a stent havingbrace elements that are aligned.

FIGS. 11A-11C illustrate an exemplary method of loading a stent onto adelivery catheter.

FIGS. 12A-12E illustrate an exemplary method of deploying a stent.

FIG. 13 illustrates an exemplary embodiment of a stent having braceelements with contoured engagement surfaces.

FIG. 14 illustrates an exemplary embodiment of a compressed braced stenthaving serpentine brace element.

FIG. 15A illustrates an exemplary embodiment of a compressed bracedstent having sinusoidal bridge.

FIG. 15B illustrates an enlarged view of the sinusoidal bridge elementof FIG. 15A.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates generally to medical devices, and moreparticularly to endoluminal prostheses such as stents, or otherimplantable structures. The stents may be placed in the arterial system,the venous system, or any other portion of the body. The stents may alsobe used to deliver drugs to tissue, support tissue, or maintain patencyof bodily lumens, as well as performing other functions, and have beenwidely reported in the scientific and patent literature.

As discussed above, longer stents may buckle or undesirably collapse dueto lack of rigidity or support. Modeling of typical stents which have aseries of rings connected together with a bridge shows that materialtensile strength, bridge width, stent wall thickness, and bridge lengthare key factors that determine the buckling force the bridge canwithstand before deformation occurs. The column strength (F) of thestent may be mathematically represented using the following equationwhere L is the length of the bridge, b is the wall thickness of thestent, h is the bridge width. Additionally, E is the stent materialmodulus of elasticity, I is the second moment of interia, and K is acolumn effective length factor, where the value depends on conditions ofend support of the column.F=π ² EI/(KL)², and I=bh ³/12

Therefore, adding a brace element to the bridge widens the bridge whichincreases the bridge second moment of inertia, thereby increasing thecolumn strength of the stent. Additionally, one of skill in the art willappreciate that column strength or buckling force may also be increasedby effectively shortening the length L of the bridges when braces areincluded.

The outward force of the stent is a function of its material properties,architecture, diameter, and other service conditions. Expandable stentsare commonly formed from a series of expandable ring members, each ofwhich is comprised of a series of strut elements disposed around thecircumference of the structure. The longitudinal connections betweenthese expandable ring members can be described as bridging members. Thenumber, design, order, and connection of these expandable ring membersand bridging members defines the overall architecture of the stent. Thestrength, stiffness, conformability, and flexibility of the stent arecontrolled by the selection and design of these expandable ring membersand bridging members.

The stiffness or strength of the stent is strongly influenced by thedesign of the expandable ring members. An expandable ring member iscommonly comprised of a series of n strut elements disposed around thecircumference of the structure. Each strut can be further described byits length L, width w, and thickness t. The stiffness of the stent k canbe approximated using a formula relating n, L, w, t, and the elasticmodulus of the material, E. Vascular stents may be subjected to twodifferent types of loading conditions in vivo. The first of these can bedescribed as hoop, circumferential, or radial loading. An arterial orvenous stent placed in a perfectly concentric lesion is an example ofthis type of loading. The stiffness of a stent subjected to such a hoopload can be approximated by the following relationship.k _(hoop)α(Ew ³ t)/(nL ³)

Thus, in this mode of loading, it is clear that the hoop stiffness isdominated by the cube of the strut width, and inversely related to thecube of the strut length. Therefore, to increase stent stiffness, widerand shorter struts may be used.

FIG. 1 illustrates an exemplary embodiment of a braced stent thatprovides enhanced rigidity and support during loading and deployment.The stent 10 is typically a cylindrically shaped structure, and has aradially collapsed configuration for delivery, and a radially expandedconfiguration for engaging and supporting tissue. FIG. 1 shows stent 10in the collapsed configuration (e.g. after loading or crimping onto adelivery catheter) after it has been unrolled and flattened out. Thestent 10 has proximal end 30 and a distal end 32, and includes aplurality of annular rings 12 interconnected together and coaxiallyaligned with one another. The rings are connected together with a bridgeelement 14. The distal end of one ring generally faces the proximal endof an adjacent ring, and the proximal end of one ring generally facesthe distal end of an adjacent ring (except for the proximal-most anddistal-most rings). In this embodiment, each ring is formed from aplurality of interconnected struts 28 that form a series of peaks 22 andvalleys 24. The peaks and valleys of one ring are preferably in-phasewith the peaks and valleys of an adjacent ring, although this is notrequired and the rings may be out-of-phase with one another. The struts28 are generally linear and generally parallel with the longitudinalaxis of the stent 10, although this is not intended to be limiting.Adjacent pairs of struts 28 are coupled together with a connectorelement 26. The connector element is preferably V-shaped or U-shaped,although other geometries may also be used. The bridge element 14includes a proximal arm 18, a distal arm 20, and a brace element 16disposed therebetween. The proximal and distal arms 18, 20 arepreferably linear struts, but any geometry may be used. The proximal arm18 is preferably coupled to a connection point on the proximal ring, andthe distal arm 20 is preferably coupled to a connection point on thedistal ring. The proximal arm preferably is coupled to the apex of apeak 22, and the distal arm is preferably coupled to the bottom or nadirof a valley 24 on the adjacent distal ring. In this embodiment, thebrace element is parallelogram shaped such that the width of the braceelement is wider than the width of the arms 18, 20. The length of thebrace element 16 is also less than the total length of the bridge 14,and the length of the brace element is longer than either the proximalor distal arm. The brace element has an upper surface 36 and a lowersurface 34. In this embodiment, the upper and lower engagement surfacesare flat and planar, such that the upper surface engages the lowersurface of an adjacent brace element on an adjacent bridge. The upperand lower surfaces engage one another in the radially collapsedconfiguration. This helps provide additional support and rigidity to thestent when it is crimped or otherwise loaded onto a stent deliverycatheter and helps reduce or prevent the likelihood of buckling. Whilethe preferred shape of the brace element is a parallelogram, one ofskill in the art will appreciate that this is not intended to belimiting, and that other geometries may also be used, such as rhomboid,trapezoidal, non-quadrilateral, rectangular, square, circular, oval,elliptical, triangular, as well as other shapes and combinationsthereof. Additionally, during stent deployment, a constraining or outerprotective sheath may be retracted causing forces to be applied to thestent. Retraction of the sheath may apply axially oriented forces to thestent that can result in buckling during deployment of the stent. Theaxially oriented forces cause the brace elements to engage one another,thereby providing better support and rigidity to the stent duringdeployment, thereby reducing the likelihood of buckling of the stent. Inalternative embodiments, the upper and lower engagement surfaces may notbe flat or planar, but they may still be contoured such that one surfacenests with the other surface, for example one surface being convex whilethe other is concave, seen in FIG. 13.

Referring to FIG. 13, stent 10 i generally takes the same form as theother stents disclosed herein, with the major difference being thatinstead of the bridge having a brace element with flat planar upper andlower engagement surfaces, the bridge 14 i has brace element 16 i withan arcuate upper engagement surface 36 i, and an arcuate lowerengagement surface 34 i. In this embodiment, the brace element 16 i isdisposed between proximal and distal arms 18 i, 20 i which are linearstruts which couple the brace element 16 i to the proximal and distaladjacent rings 12. The upper engagement surface 36 i has a convex regionsurrounded by concave regions, and the lower engagement surface 34 i hasa concave region surrounded by convex regions. Thus, the convex regionof the upper engagement surface will engage and nest with the concaveregion on an adjacent lower engagement surface when the stent is in thecollapsed configuration. One of skill in the art will appreciate thatother contoured surfaces may also be used to nest with one another.

Referring back to the embodiment of FIG. 1, a bridge having a braceelement connects each peak on one ring with each valley on an adjacentring. The proximal and distal connection points are circumferentiallyoffset from one another such that the bridge is angled or transverserelative to the longitudinal axis of the stent. FIG. 1 also illustrateshow the slope of bridges alternate between adjacent rings. For example,the bridges generally have a positive slope between the first and secondproximal-most rings, while the bridges between the second and thirdproximal-most rings have a negative slope. Additionally, the braceelements on bridges between adjacent rings are axially andcircumferentially aligned so that the brace elements are substantiallyparallel with one another and aligned in a single circumferentiallyoriented column. This embodiment has five rings, and four columns ofbridges. The stent may be balloon expandable, or in preferredembodiments is self-expanding. Balloon expandable stents are typicallyfabricated with 316L stainless steel, or cobalt chromium alloy, whileself-expanding stents are often fabricated from a nickel titanium alloysuch as Nitinol. One of skill in the art will appreciate that othermaterials such as resilient polymers, biodegradable materials, or othermaterials may be used to fabricate the stent. The stent is preferablylaser cut from a tube such as a hypotube, or it may be electricaldischarge machined (EDM) from a tube, photochemically etched from a flatsheet rolled into a cylinder and welded together. It is preferably anintegral component, although it may be fabricated from several segmentsthat are coupled together (e.g. by welding or bonding).

FIG. 2 illustrates the stent 10 of FIG. 1 in the radially expandedconfiguration. The rings 12 radially expand, therefore struts 28 open upand angulate away from the adjacent strut. This results in an increasein the stent diameter. Additionally, bridges 14 also move away from oneanother such that the upper engagement surface 36 no longer engages thelower engagement surface 34 of the adjacent brace. In the radiallyexpanded configuration, the stent engages and supports tissue (e.g.supports a vessel wall). Therefore, the additional structural support inthe compressed form from the braces contacting each other is lost whenthe stent is expanded because the contact between braces is no longerpresent. However, some added strength and rigidity remains in theexpanded form due to the increase in bridge width in the braced areas.

FIG. 3 illustrates another exemplary stent embodiment that is similar tothe embodiment of FIG. 1, with the major difference being the braceelement 16 a on the bridge 14 a. In this embodiment, the brace element16 a is shorter than the brace element 16 in FIG. 1, therefore upper andlower engagement regions 36 a, 34 a are still flat and planer, butcorrespondingly shorter in length. Other aspects of stent 10 a generallytakes the same form as stent 10 in FIG. 1. In this embodiment, the braceelements 14 a are still parallelogram shaped, however, the length of thebrace element 14 a is shorter than either of the arms 20 a, 18 a oneither side thereof. The width of the brace element is still wider thanthe width of arms 20 a 18 a. Brace elements 14 a are aligned axially andcircumferentially between adjacent rings so as to form a single columnof aligned brace elements where upper and lower engagement surfacesengage the adjacent engagement surface of an adjacent brace element toprovide additional rigidity and support to the stent during deploymentor during loading onto a delivery system.

FIG. 4 illustrates another exemplary stent embodiment that is similar tothe embodiment of FIG. 1, with the major difference being that thebridges each have two brace elements. In this embodiment, each bridge 14b includes three arms 18 b, 19 b, 20 b formed from linear struts. Abrace element 16 b is disposed between adjacent arms. Thus arm 18 b iscoupled preferably to the apex of a peak 22 on one ring, and arm 20 b ispreferably coupled to the nadir of a valley 24 on the adjacent ring. Twobrace elements 16 b are coupled to arms 18 b, 20 b, and disposed betweenadjacent rings. A third arm 19 b separates the two brace elements 16 b.In this embodiment, both brace elements are the same geometry, hereparallelogram shaped, however in alternative embodiments the braceelements may be different from one another. In this embodiment, thewidth of each brace element is wider than the width of the strutsforming the arms, and the length of each brace element is less than thelength of each arm. The brace elements are circumferentially and axiallyaligned so as to form two columns of aligned brace elements. Also, inthis embodiment, the bridges will have two upper and two lowerengagement surfaces 34 b, 36 b that engage the adjacent engagementsurface in an adjacent bridge when the stent is radially collapsed or anaxially oriented force is applied thereto. As in the other embodimentsdescribed herein, this helps stabilize the stent and rigidify the stentduring loading onto a delivery system or during delivery. Other aspectsof this embodiment generally take the same form as the embodiments inFIGS. 1-3 above.

FIG. 5 illustrates another exemplary embodiment of a braced stent 10 c.The stent 10 c is similar to previous embodiments, with the majordifference being that the brace element 16 c is not solid, and has aslotted region 38 extending through the thickness of the brace. Theslotted region 38 is preferably rectangular or parallelogram shaped andit may be laser cut, EDM machined, photochemically etched, or otherwiseformed in the stent so that the brace element has upper and lowerelongate linear struts that form the upper and lower engagement surfaces36 c, 34 c for engaging an adjacent engagement surface on an adjacentbrace element. The brace element 16 c is coupled to two arms 18 c, 20 cwhich are formed from linear struts that are connected to an adjacentpeak 22 and valley 24 on adjacent rings 12. Brace elements 16 c areaxially and circumferentially aligned with one another to form a singlealigned column of brace elements disposed between adjacent rings. Otheraspects of stent 10 c generally take the same form as those ofembodiments previously described above. The geometry of the slottedregion may be adjusted in order to provide the stent with desiredmechanical properties.

The embodiment of FIG. 6 is similar to previous embodiments, with themajor difference being that instead of the brace elements being alignedto form a single aligned column of brace elements between adjacentrings, the brace elements are axially displaced relative to one anotherso that a staggered column of braces is formed between adjacent rings.Stent 10 d generally takes the same form as the embodiments describedabove, but bridges 14 d include a brace element 16 d with upper andlower engagement surfaces 36 d, 34 d disposed between arms 18 d, 20 dformed from linear struts that are coupled to the peaks 22 and valleys24 of adjacent rings 12. Each brace is axially displaced relative to anadjacent brace so that the brace elements 16 d form an alternating orstaggered column of brace elements 16 d between adjacent rings. Thus,only a portion of the upper engagement surface 36 d engages only aportion of the lower engagement surface 34 d. The entire engagementsurfaces do not contact one another in this embodiment. Other aspects ofthe stent 10 d generally take the same form as those described above.

FIG. 7 illustrates another embodiment of a braced stent that is similarto those described above, with the major difference being that in thisexemplary embodiment, the brace element is only on every other bridgebetween adjacent rings. Stent 10 e generally takes the same form asthose described above, except that every other bridge 14 e includes abrace element 16 e disposed between the two arms 18 e, 20 e, which areformed from linear struts connected to a peak 22 and a valley 24 onadjacent rings 12. A linear strut 23 is disposed between adjacentbridges 14 e having brace elements, and one end of the linear strut 23is coupled to a peak 22, while the opposite end is coupled to a valley24. The brace elements 16 e are aligned so as to form a single alignedcolumn of brace elements between adjacent rings 12. The brace elements16 e are parallelogram shaped in this embodiment, but may be othershapes as well. The brace elements include an upper engagement surface36 e, and a lower engagement surface 34 e that are both flat planarregions. Unlike other embodiments where an upper engagement surfaceengages a lower engagement surface of an adjacent brace element, in thisembodiment the upper engagement surface engages an inferior surface of alinear strut 23 and the lower engagement surface engages a superiorsurface of a linear strut 23 when the stent is in a radially collapsedconfiguration, such as when a radially inward force is applied to thestent, or when an axially oriented force is applied to the stent. Thebridges 14 e are generally parallel with one another, and the linearstruts 23 are also generally parallel with one another. Just as inearlier embodiments the slope of the bridges alternates between apositive and negative slope, the slope of the linear strut 23 similarlyalternates between a positive and negative slope. Additionally, becausethe brace elements are only on every other bridge, the brace element iswider than the width of the arms 18 e, 20 e, and the brace element isalso wide enough to engage an adjacent brace element.

FIG. 8 illustrates another embodiment of a stent having bracedconnectors. Stent 10 f is substantially similar to previous embodimentswith the major difference being that in this embodiment, a bridge 14 fonly connects every third peak 22 to every third valley 24 of anadjacent ring 12. This requires fewer bridges than previous embodiments,and that may provide a stent that has greater flexibility betweenadjacent rings, and also reduces the amount of metal or other materialthat is implanted in a patient, while still providing the necessarysupport and rigidity to the stent during loading or deployment. Stent 10f generally takes the same form as previous stents described above, andhas a plurality of interconnected rings 12. Adjacent rings are connectedwith a bridge 14 f having arms 18 f, 20 f that are connected to a peakor valley 22, 24. Each bridge 14 f includes a brace element 16 f thatgenerally has a parallelogram shape that is wider than the width of thearms 18 f, 20 f, and the length of the brace element 16 f is shorterthan the length of the linear struts which form arms 18 f, 20 f. Theupper engagement surface 36 f of a brace element engages the lowerengagement surface 34 f of an adjacent brace element. In thisembodiment, the upper and lower engagement surfaces 34 f, 36 f are flatplanar surfaces, although as describe above, the engagement surfaces maybe contoured to nest with one another (e.g. a concave surface and aconvex surface).

FIG. 9A illustrates another embodiment of a braced stent. Thisembodiment is similar to the embodiment of FIG. 4, with the majordifference being that the proximal and distal ends of each brace elementare tapered thereby smoothing leading edges that potentially providesharp edges which may cause trauma to the tissue, or may get hung on ordamage a portion of the delivery catheter either during delivery or inthe event the stent needs to be recaptured prior to full deployment.Stent 10 g includes two brace elements on each bridge 10 g. The bridge10 g includes three arms 18 g, 19 g, 20 g. Arms 18 g and 20 g have oneend coupled to a peak 22 or valley 24 in a ring 12, and the opposite endof arm 18 g and 20 g is coupled to one end of a brace element 16 g. Thetwo brace elements 16 g are separated from one another, and coupled tothe third arm 19 g. A bridge couples every peak and valley in adjacentrings. The three arms are formed from a linear strut. The length of thebrace element is preferably longer than the length of the arms in thebridge, and the width of the brace element is also preferably wider thanthe width of the linear struts which form the arms. The leading andtrailing edges 40 (proximal and distal ends) of each brace element aretapered to smooth out sharp corners and edges. In this embodiment, theedges are beveled. In alternative embodiments, a radius may be used tosmooth the leading edges of the parallelogram shaped brace. Each braceelement also has an upper and lower engagement surface 36 g, 34 g thatengages an adjacent engagement surface. In this embodiment, theengagement surfaces are flat and planar, but they may take any of theforms described herein. Other aspects of the stent 10 g generally takethe same form as those of the other stents described herein.

In various embodiments, the bridge elements may include a single braceelement or multiple brace elements. FIG. 9B illustrates anotherexemplary embodiment of a stent having a single brace element on aconnector. The bridge element 14 j includes a proximal arm 18 j, adistal arm 20 j, and a brace element 16 j disposed therebetween. Thestent 10 j of FIG. 9B is similar to the stent 10 g of FIG. 9A exceptthat the bridge element 14 j includes a single brace element 16 j as inFIGS. 1 and 3. The brace element 16 j includes proximal and distal endsthat are tapered to create smoothing leading and trailing edges 40 as inthe brace element 16 g of FIG. 9A. The brace element 16 j also includesan upper and lower engagement surface 36 j, 34 j that engages anadjacent engagement surface.

Stent 10 j has a proximal end 30, a distal end 32 and includes aplurality of annular rings 12 interconnected together and coaxiallyaligned with one another. The annular rings 12 are similar to theannular rings of FIGS. 1, 3-9A, 13, and 14. The annular rings 12 includestruts 28, peaks 22 and valleys 24 and may be interconnected betweenbridge elements 14 j. The struts are generally linear and generallyparallel with the longitudinal axis of stent 10 j. The slope of thebridge elements 14 j between the annular rings 12 is similar to theslope of bridge elements 14 in stent 10 of FIG. 1.

FIG. 10 illustrates still another exemplary embodiment of a brace stent.Stent 10 h is similar to previous stents described above, with the majordifference being that the brace elements on bridges are aligned to formaligned rows of brace elements between adjacent rings. Stent 10 hincludes a bridge 14 h between adjacent rings 12. A bridge 14 h iscoupled to each peak 22 and each valley 24 in adjacent rings. However,not every bridge 14 h includes a brace element 16 h. Thus some bridges14 h comprise only a linear strut 23 h, while other bridges 14 h includea brace element 16 h coupled to, and disposed between adjacent arms 18h, 20 h. Arms 18 h, 20 h are coupled to an adjacent peak or valley 22,24. Additionally, in this embodiment, the brace elements are arranged onthe bridges such that they are circumferentially aligned with oneanother to form an aligned row of axially oriented brace elementsbetween adjacent rings. This embodiment has two rows of brace elementsbetween adjacent rings. Because of the alignment of the brace elements,the engagement surfaces of the brace elements are now proximal anddistal lateral engagement surfaces 44 h, 42 h, unlike other embodimentswhere the engagement surfaces are upper and lower surfaces of the braceelement. Additionally, due to the use of brace elements only on selectedbridges, the lateral engagement surfaces 44 h, 42 h engage an adjacentlinear strut 23 h when the stent 10 h is collapsed during loading, orwhen an axially oriented force is applied to the stent duringdeployment. Other aspects of the stent 10 h generally take the same formas stents previously described above. The lengths of the arms 18 h, 20 hvary along different bridges due to the alignment of the brace elements.However, in general, the length of one set of arms (e.g. 20 h) willshorten while the length of the other set of arms (e.g. 18 h) willlengthen.

FIG. 14 illustrates an exemplary embodiment of a compressed braced stenthaving serpentine brace element. Stent 10 k is similar to previousstents described above, with the major difference being that the bridgeelement 14 k has a brace element 16 k in a serpentine shape. Within theserpentine shape, the portion forming the brace may be a meandering,zig-zag, step-like, wave-like, undulating, or angled pattern wherein theedges forming the serpentine shape are in contact or in close proximityto each other. The bridge element 14 k includes a proximal arm 18 k, adistal arm 20 k, and a brace element 16 k in between the proximal arm 18k and the distal arm 20 k. The proximal arm 18 k and distal arm 20 k aresimilar to those illustrated in FIGS. 1 and 3 with respect to theirgenerally linear geometry and attachment to the apex of the peak 22 andthe bottom of valley 24 of an adjacent ring 12. In one aspect, thelengths of each of the proximal arms 18 k and the distal arms 20 k areless than the length of the brace elements 16 k. The proximal end 46 andthe distal end 48 of the brace elements 16 k may be radiused. Theproximal end 50 of the distal arm 20 k and the distal end 52 of theproximal arm 18 k may be angled as shown in FIG. 14. The adjacent bridgeelements 14 k may also be in contact or in close proximity to eachother.

Stent 10 k also has a proximal end 30, a distal end 32 and includes aplurality of annular rings 12 interconnected together and coaxiallyaligned with one another. The annular rings 12 are similar to theannular rings of FIG. 1. The annular rings 12 include struts 28, peaks22 and valleys 24 and may be interconnected between bridge elements 14k. The struts are generally linear and generally parallel with thelongitudinal axis of stent 10 k. The slope of the bridge elements 14 kbetween the annular rings 12 are similar to the slope of bridge elements14 in stent 10 of FIG. 1.

FIG. 15A illustrates an exemplary embodiment of a compressed bracedstent having sinusoidal bridge. The stent 60 of FIG. 15 includes similarcomponents of interconnected bridge elements 62, annular rings 64, aproximal end 30 and a distal end 32 of FIG. 10. Stent 60 differs fromother stent embodiments described herein in that stent 60 does notinclude a brace element. Contrary to FIGS. 1-10, 13 and 14, the bridgeelements 62 include an arm which extends the full length of bridgeelements 62. Bridge element 62 is discussed in more detail below withrespect to FIG. 15B. Each end of the sinusoidal bridge element 62 isconnected to an adjacent annular ring. The bridge elements 62 may be incontact or in close proximity to each other. The slope of the bridgeelements 62 between the annular rings 64 may be similar to the slope ofbridge elements 14 in stent 10 of FIG. 1.

Each annular ring 64 is formed from a plurality of interconnected strutsthat form a series of peaks 68 and valleys 70. Because of the shape andalignment of the bridge elements 62, the peak 68 may be formed from anupper strut 72 and a lower strut 74. In various embodiments, the upperstrut 72 and lower strut 74 are generally linear and not parallel toeach other, such that they may be separated and may only be in contactwith each other at peaks 68.

FIG. 15B illustrates an enlarged view of the sinusoidal bridge elementof FIG. 15A. Sinusoidal bridge element 66 includes sections 66 a, 66 b,66 c, 66 d, 66 e and 66 f and bends 66 g, 66 h, 66 i, 66 j, and 66 k.Each section connects at a bend, and each bend is positioned between andformed by two adjacent sections. For instance, bend 66 g is positionedbetween sections 66 a and 66 b. Each bend has an inner angle “a” and anouter angle “b”. In some instances, the inner angle “a” may be less thanthe outer angle “b” when the stent is unexpanded. The angulations of thearms may form at least one sinusoidal cycle along the length of thebridge element 62. The arm sections 66 a-f and bends 66 g-k may alsoform a pattern such as, but not limited to, a meandering, zig-zag,step-like, wave-like, undulating, or angled pattern, each of which mayalso form one or more cycles along the length of the bridge element 62.

As discussed above, the stents described herein may be balloonexpandable, self-expanding, or a combination thereof. Preferably, thestents are self-expanding, and they are preferably formed fromsuperelastic material. In one specific aspect, the superelastic materialis Nitinol, an intermetallic compound having approximately 50.8 atomicpercent Nickel and the balance Titanium. Nitinol has the uniqueproperties of shape memory and superelasticity, and in this applicationis designed to take advantage of the material's ability to withstandunusually high levels of strain (up to 8% or more), without experiencingplastic deformation. The material can have an unusually pronouncedhysteresis effect in its stress-strain relationship: when subjected toloading, stresses are relatively high, as they reach the upper plateau(UP) where a phase change from austenite to martensite occurs. When thematerial is unloaded, stresses are relatively low, as seen in the lowerplateau (LP) where the material transforms from martensite to austenite.The magnitude of the difference between UP and LP stresses is determinedby material composition, as well as thermal and processing history. Inthis application, the transition temperature for the material, known asthe Austenite Finish (A_(f)) temperature is preferably set between 10degrees and 40 degrees, and more preferably set to between 10 degreesand 37 degrees C. Preferentially, the A_(f) temperature is set close tobody temperature to maximize the hysteresis effect of the material,increasing the difference between UP and LP. As such, forces exerted bythe stent as it unloads (expands) from its constrained state areminimized: this force, described as Chronic Outward Force (COF), iscontrolled by the LP stress. Conversely, the forces exerted by the stentwhen it is loaded (subjected to external compression) are maximized:this force, described as Radial Resistive Force (RRF), is controlled bythe UP stress.

Any of the stent embodiment disclosed herein may also be used to delivera therapeutic agent from the stent to tissue. Exemplary therapeuticagents include anti-restenosis agents such as paclitaxel, rapamycin andanalogs thereof such as everolimus, biolimus A9, etc., or otheranti-stenosis agents known to those of skill in the art. Othertherapeutic agents may include anti-thrombogenics/anti-thrombolyticssuch as heparin, tissue plaminogen activator (tPA), as well as othertherapeutic agents such as antibiotics, etc. One of skill in the artappreciates that these agents may be coated, layered, or otherwiseapplied to the stent using known methods so that the agent may becontrollably eluted therefrom.

FIGS. 11A-11C illustrate an exemplary method of loading any of the stentembodiments disclosed herein onto a delivery catheter. In FIG. 11A,stent 202 is in its unbiased, radially expanded configuration. Thedelivery system includes a central shaft 206 having an outerconstraining sheath 204 slidably disposed thereover. A radially inwardforce 208 is applied to stent 202 in FIG. 11B, and an axially orientedforce 210 is used to simultaneously push and compress stent 202 overinner shaft 206, and under sheath 204. This process is continued untilthe stent is 202 is constrained from expansion by sheath 204, as seen inFIG. 11C. It is during this loading process that the brace elements ofthe stent (not shown) engage one another and prevent the stent fromunwanted deformation such as buckling. Once loaded onto the deliverycatheter, the stent may be delivered to a desired treatment site. Thestents disclosed herein may be used to treat any number of diseases. Inan exemplary method of usage, the physician will gain intraluminalaccess to the target location of the anatomy using standard techniques(e.g. percutaneous techniques such as the Seldinger technique, orcutdown methods), and may perform diagnostic imaging to help identifythe location and extent for the need of stenting. Diagnostic imaging mayinclude x-ray or fluoroscopy, endoscopy, magnetic resonance, ultrasound,intravascular ultrasound (IVUS), and computed tomography.

In the preferred method of use, the delivery system is used to treatvascular disease, specifically venous disease (i.e. iliac veincompression syndrome, post-thrombotic syndrome) to improve venousoutflow. In a preferred embodiment, the device is hand-held by the user.The user inserts the device in the pelvic venous region using standardintravascular techniques. The stent is constrained within a flexibleinner and outer sheath, preferably such that the outer sheath iscompatible with an introducer sheath having a profile of 10 French orless. Typically, the physician will have already placed a 0.035″guidewire across the site of the target vessel during balloon venographyprior to stenting. The physician then advances the stent delivery systemover such a guidewire to the target site, and positions the stent in thedesired location using x-ray and/or ultrasound guidance. After the stenthas initially expanded and been anchored in the vessel, it may beadvantageous to confirm accurate placement with the use of imaging(IVUS, or x-ray guidance). If the placement of the stent is not optimal,the physician may re-advance the constraining outer sheath to recapturethe deployed segment of stent, reposition the delivery system, andattempt the deployment again. After the stent has been confirmed to beanchored in the intended location, the outer sheath is fully retracted,releasing the entire stent from the delivery system. The fully expandedstent is now in its final position within the iliac or femoral vein.

As a final step, it may be advantageous to inflate a balloon within thestent, particularly in the region of the obstructive lesions. With thismethod, the stent's outward resistive forces are maximized to ensuremaximum luminal gain and relief from the symptoms associated withvascular disease. This post-dilation also helps to ensure that theexpanded stent is fully tacked into position and into engagement withthe vessel wall or other target tissue. Other aspects of exemplary stentdelivery methods and exemplary delivery systems are disclosed incopending U.S. patent application Ser. No. 12/903,056 filed Oct. 12,2010, and Ser. No. 12/911,604 filed Oct. 25, 2010, the entire contentsof each is incorporated herein by reference.

It would also be desirable to provide an intravascular ultrasound (IVUS)catheter that is designed to work in conjunction with the stent anddelivery system described herein. Preferentially, the IVUS probe wouldbe contained within the profile of a standard 0.035″ guidewire, andcould therefore be used to replace the conventional guidewire forballoon and stent delivery while providing opportunity for imagingthroughout the procedure.

FIGS. 12A-12E illustrate the basic steps of stent deployment in anexemplary embodiment used to treat venous compression syndrome. FIG. 12Aillustrates the target treatment region of a vein V that is compressed302 due to externally applied forces from an adjacent vessel, ligament,tumor, or other tissue. The delivery catheter which comprises a centralelongate shaft 206, outer constraining sheath 204 and stent 202 arepercutaneously introduced into the vessel and transluminally advanced tothe treatment site as seen in FIG. 12B. The outer sheath 204 isproximally retracted 304 as illustrated in FIG. 12C and then stent 202begins to self-expand as shown in FIG. 12D. During sheath retraction,friction between the stent and sheath may result in axially orientedforces which can cause the stent to deform or buckle in an undesiredfashion. However, the axially oriented forces may also cause the braceelements of the stent to engage one another, thereby providingadditional support and rigidity to the stent, thereby preventingunwanted deformation. The outer sheath is fully refracted until stent202 is fully expanded into engagement with the vessel, alleviating thecompression 302 caused by the external forces. The delivery catheter maythen be retracted and removed from the patient.

Although the exemplary embodiments have been described in some detailfor clarity of understanding and by way of example, a variety ofadditional modifications, adaptations and changes may be clear to thoseof skill in the art. One of skill in the art will appreciate that thevarious features described herein may be combined with one another orsubstituted with one another. Hence, the scope of the present inventionis limited solely by the appended claims.

What is claimed is:
 1. A stent comprising: a plurality of radiallyexpandable rings each having a contracted configuration suitable fordelivery and a radially expanded configuration for engaging andsupporting tissue, wherein each ring is formed from a plurality ofinterconnected struts, adjacent struts in each ring being connectedtogether with a connector, and each ring having a proximal end, and adistal end, wherein the plurality of rings is coaxially aligned with oneanother to form a longitudinal axis, wherein a distal end of one ringfaces a proximal end of an adjacent ring; and a plurality of bridgesdisposed between adjacent rings, the plurality of bridges couplingadjacent rings together, wherein one or more bridges of the plurality ofbridges comprise a first end, a second end, and a first brace elementtherebetween, wherein the first end of the one or more bridges iscoupled with the distal end of a first ring at a first connection point,and the second end of the one or more bridges is coupled with theproximal end of an adjacent second ring at a second connection point;the first brace element of each of the one or more bridges having aproximal end and a distal end and an intermediate section therebetween,at least one of the proximal end or the distal end of the first braceelement having a tapered edge, the one or more bridges comprising afirst arm and a second arm, the first brace element being wider than thefirst arm or the second arm and the first brace element being disposedtherebetween, the first and second arms having flat and planar upper andlower surfaces, the tapered edge increasing in width from a respectiveend of the first arm or second arm to the first brace element along theproximal end or the distal end of the first brace element, the firstbrace element having a width that is wider than a width of the struts ofthe corresponding adjacent rings, the intermediate section of the firstbrace element having an upper engagement surface and a lower engagementsurface each adjacent the tapered edge; and wherein the upper engagementsurface of the intermediate section of the first brace element of onebridge engages the first brace element of an adjacent bridge and alignssubstantially along an entire length of the lower engagement surface ofthe intermediate section of the first brace element of the adjacentbridge when the corresponding adjacent rings are in the contractedconfiguration.
 2. The stent of claim 1, wherein the plurality ofinterconnected struts form a series of peaks and valleys.
 3. The stentof claim 2, wherein the peaks and valleys of the first ring are in phasewith the peaks and valleys of the adjacent second ring.
 4. The stent ofclaim 2, wherein the connector interconnecting the plurality of strutsis U-shaped or V-shaped.
 5. The stent of claim 1, wherein the rings areself-expanding.
 6. The stent of claim 1, wherein the rings are balloonexpandable.
 7. The stent of claim 1, wherein the first connection pointof a bridge of the one or more bridges is circumferentially offsetrelative to the second connection point of the bridge so that the bridgeis at an angle to the longitudinal axis.
 8. The stent of claim 1,wherein the tapered edge forms at least one of a smooth leading taperededge or smooth trailing tapered edge for the first brace element.
 9. Thestent of claim 1, wherein the first arm or the second arm, or both,comprises a linear strut.
 10. The stent of claim 1, wherein the firstarm and the second arm each have a width, and the first brace elementhas a width that is wider than the width of the first arm and the secondarm.
 11. The stent of claim 2, wherein the first connection point is ona peak of the first ring, and the second connection point is on a valleyof the adjacent second ring.
 12. The stent of claim 1, wherein the oneor more bridges couples a pair of adjacent struts interconnectedtogether in the first ring with a pair of adjacent struts interconnectedtogether in the adjacent second ring or an adjacent third ring.
 13. Thestent of claim 1, wherein the first brace element comprises aparallelogram shaped region.
 14. The stent of claim 1, wherein the upperengagement surface of the intermediate section of the first braceelement of the one bridge has a first contour and the lower engagementsurface of the intermediate section of the first brace element of theadjacent bridge has a second contour, the first contour nesting with thesecond contour when the corresponding adjacent rings are in thecontracted configuration.
 15. The stent of claim 1, wherein the firstbrace elements on the one or more bridges disposed between the adjacentrings are circumferentially aligned with one another to form an axiallyoriented row of first brace elements.
 16. The stent of claim 1, whereinthe first brace element on a first bridge of the one or more bridges isaxially offset relative to the first brace element of a second bridge ofthe one or more bridges on an adjacent ring.
 17. The stent of claim 16,wherein the first brace elements of bridges of the one or more bridgesdisposed between a pair of adjacent rings form a circumferentiallystaggered pattern.
 18. The stent of claim 1, wherein a first bridge ofthe plurality of bridges couples the first ring and the second adjacentring, and a second bridge of the plurality of bridges couples the secondring with a third ring adjacent the second ring, and wherein the firstbridge has a positive slope relative to the longitudinal axis, and thesecond bridge has a negative slope relative to the longitudinal axis.19. The stent of claim 1, wherein the upper engagement surface of theintermediate section of the first brace element of the one bridge doesnot contact the lower engagement surface of the intermediate section ofthe first brace element of the adjacent bridge when the correspondingadjacent rings are in the radially expanded configuration.
 20. The stentof claim 1, wherein the plurality of bridges disposed between adjacentrings are substantially parallel with one another.
 21. The stent ofclaim 1, wherein the first brace element comprises a length shorter thana length defined between the first end and the second end of therespective bridge.
 22. The stent of claim 1, wherein at least some ofthe one or more bridges comprise a plurality of brace elements.
 23. Thestent of claim 1, wherein a pair of the one or more bridges each havinga first brace element and joining two adjacent rings are separated by abridge of the plurality of bridges without a first brace element andjoining the two adjacent rings.
 24. The stent of claim 1, wherein atleast some of the plurality of interconnected struts are not connectedto a bridge.
 25. The stent of claim 1, wherein the tapered edge is atleast one of rounded or beveled.
 26. The stent of claim 10, wherein theintermediate section has a width defined between the upper engagementsurface and the lower engagement surface, the width of the intermediatesection greater than the width of each of the first and second arms, andthe tapered edge having a longitudinally variable width that is thewidth of the intermediate section at one end and the width of the firstarm or the second arm at an opposite end.
 27. The stent of claim 1,wherein the intermediate section has a uniform width along a length ofthe intermediate section between the proximal and distal ends of therespective first brace element, the width defined between the upperengagement surface and the lower engagement surface of the intermediatesection.
 28. The stent of claim 1, wherein the plurality of bridgesextend linearly between adjacent rings.